Web tension control means



Oct. 9, 1962 E. J. JUSTUS WEB TENSION CONTROL MEANS Filed Aug. 8, 1960 Wm 7 1 F M; A Hm INVENTOR.

m u d r r WY d 5 W 3,057,574 WEB TENSION CONTRGL MEANS Edgar J. Justus,lieloit, Wis, assignor to Beloit Iron Works, Beloit, Wis, a corporationof Wisconsin Filed Aug. 8, 1966, Ser. No. 48,236 9 Claims. (til.242-7543) The present invention relates broadly to the winding of sheetmaterials, and is more particularly concerned with means for controllingthe tension in a web or strand being supplied to processing apparatusfrom a supply or unwind roll.

It is of course well known that the tension of a web or strand beingunwound from a non-driven supply roll is limited by the strength of theweb or by its strain properties, and that the web may be damaged andrendered unfit for its best intended use even when the strain is lessthan breaking strain. As is also known, the web strength properties orstrain characteristics are essentially fixed or constant for aparticular web or strand.

On the other hand, the force required to unwind the web from thenon-driven supply roll and applied by means of tension is dependent upona number of factors, an important one of which is the size of the roll.In addition, the dictates of efiiciency and high production ratesrequire a rapid acceleration of the supply roll from a rest condition tothe desired operating speed of the unit being served thereby. It isfurther known that the inertia of the supply roll must be overcome by anacceleration torque, which is the product of web tension and rollradius, and accordingly limited by the stated necessity that the tensionapplied be less than that which could cause web damage. Further, sincethe roll inertia is a function of the square of the roll radius, itfollows that larger rolls cannnot be accelerated at the rates tolerablewith rolls of lesser diameter.

It is a requirement of the art that a successful unwinding systemprovide for control of several sizes of supply rolls, as Well as startand stop operations on a single roll. There is accordingly in use supplyroll systems having friction brake arrangements in which the brakingefforts are reduced or removed by a constant force, as exemplified byspring means. The same friction brake arrangement then increases orapplies the braking eifort by a modulated force, such as may be providedby a fluid diaphragm or cylinder. The two forces are in opposition, sothat at zero braking effort there is required a positive output from themodulating control.

Now, in this arrangement the braking system is modulated as a directfunction of the web tension. However, experience with this system hasdemonstrated inadequacy in coping with web tensions produced duringacceleration, particularly when the tension results from inertia of thesupply roll rather than from the braking effort. In other words, themodulated fluid pressure in such event is less than the zero or nullmentioned and no braking elTort is applied. In attempts to avoid webdamage under the stated conditions, the operator must at least payextremely close attention to his apparatus, as Well as possess skill incontrol of the winder drive. As a further expedient in avoiding webdamage the available power input to the drive unit has been limited to avalue suited to the tolerable acceleration of the weakest web or strandwhich might be wound, thus being too slow for stronger webs. It isimmediately apparent that such attempts at successful winder operationcan never result in maximum production efliciencies.

It is accordingly an important aim of the instant invention to provideweb tension control means effectively overcoming the named prior artproblems.

Another object of this invention lies in the provision of a simple,automatic and highly reliable web tension con- Patented Oct. 9, 1962trol system productive of constant sheet tension and permitting greateracceleration rates to be used with smaller diameter rolls than withlarger diameter rolls, to thereby markedly increase the output of theapparatus.

Other objects and advantages of the invention will become more apparentduring the course of the following description, particularly when takenin connection with the accompanying drawings.

In the drawings, wherein like numerals designate like parts throughoutthe same:

FIGURE 1 is a more or less diagrammatic view of web tension controlmeans constructed in accordance with the principles of this invention;and

FIGURE 2 is a vertical sectional view of a fluid pressure responsivevalve which may be employed in the system of FIGURE 1. I

Referring now to FIGURE 1, there is shown a supply or unwind roll 10from which a strand or Web 11 of paper or like materials is unwound orpulled, the web ll passing during its travel beneath a guide roll 12,over a tension sensing shoe or bleed valve means 13, between a pair ofrolls l4 and 15, and over a guide shoe 16 to a rewinder assembly 17. Therewinder assembly 17 may be seen to comprise a rewind or delivery roll18 supported upon and driven by a pair of rolls l9 and 20,diagrammatically shown as connected to motor means 21 and 22 to berotatably driven thereby.

The supply roll ltl is non-driven, and is provided with shaft means 23the rotative speed of which is under control of friction brake means,generally designated by the numeral 24. The exemplary form of brakemeans illustrated may comprise a pair of brake shoes 25 and 26 supportedthrough shaft means 27 and 28 by lever arms 29 and 30, which are in turnconnected to link members 31 and 32 pivotally mounted at 33 and 34 tostand structure 35, fixedly mounted as shown.

The upper ends of the lever arms 29 and 30 are apertured to receivetherethrough bolt means 36 to support on the lever arm 29 air brakemeans 37. The air brake means or fluid pressure actuated motor may takethe form of a brake diaphragm the construction of which is well known inthe art, and accordingly need not be further described herein. It may beobserved in FIGURE 1 that the bolt means 36 further has an enlargedportion 38 thereon, and bottoming at one end against the enlargedportion 38 is spring means :39, which encircles the bolt means 36 andbottoms at its opposite end against the lever arm 30.

In the manner known to the art, braking elforts are reduced or removedby the constant force provided by the spring means 39, while the brakingefforts are increased or applied by the modulated force provided by thebrake diaphragm 37. It is to be observed that the spring means 39 exertsforces in opposite directions against the lever arm 30 and enlargedportion 38, and the latter force is opposed by the force exerted by thelever arm 29 through the brake diaphragm 37. Accordingly, to obtain anybraking eifort a positive output is required from the modulatingcontrol, to be later described. Illustratively, the absorbing force ofthe spring means 3 9 may be ten pounds per square inch, and the brakingetfort by the brake diaphragm 37 may be in the range of ten to fiftyp.s.i. Any braking effort would therefore require ten p.s.i. or more tobe applied to the diaphragm 37.

In Patent 2,755,032, issued July 17, 1956, in the name of the instantapplicant and assigned to the assignee of the present application, thereis disclosed and claimed a web tension control system incorporating manyof the elements thus far described in this application. Since theinstant invention is particularly directed to novel means forcontrolling the acceleration of the supply roll 10 by controlling thepower delivered by the motor means 21 and 22 in response to the brakingeffort, the modulation system in control of the braking effort in thenoted Justus patent has been simplified to facilitate the instantdescription.

As appears in my patent in greater detail, a suitable air pressuresource communicates with an air source line 40 connected to header 41which has positioned therein an air pressure gauge 42 and air pressureregulator 43 in control of the pressure supply to the tension sensingshoe 13. The air source line 40 further leads to a header 44 supplyingair pressure responsive valve means 45, the structure of which alsoappears in my noted patent, but which Will be later reviewed herein whenspecific reference is made to FIGURE 2.

The header 44 has positioned therein an air pressure gauge 46 and an airpressure regulator 47, and also in this header is a by-pass gate valve48, which as is described in Patent No. 2,755,032 is in an open positionduring manual operation of the system to by-pass the valve 45, and in aclosed position during automatic operation.

The header 44 is tapped through a suitable T-connection to supply airpressures through conduit means 49 to the valve means 45 duringautomatic operation when the by-pass valve 48 is closed. As well, thereleads to the upper portion of the valve means 45 a header 50 foractuating a diaphragm therein, to be later described, in response tosignal air pressure from header 51 in fluid communication with thetension sensing shoe 13. The signal ,air pressure header 51 furtherconnects with a signal header 52 leading to the lower portion of thevalve means 45, and in control of a second diaphragm to provide a valvedamping etfect, which will be more fully understood when later referenceis made to FIGURE 2.

The signal header 51 is tapped by a header 53 leading to a surge tank 54and connected to the header 53 is a throttle valve 53a and a surge tanksignal header 55 terminating in the lower portion of the valve means 45,and acting against the second diaphragm. Air pressures in control of thebrake diaphragm 37, as well as the acceleration control means of thisinvention and to be later described, are supplied from the valve means45 through an automatic control header 56. The header 56 has a firstconduit means 57 connected thereto and leading to the brake diaphragm 37as shown.

Referring briefly now to FIGURE 2, the valve 45 has a valve body 60 inwhich is mounted cooperatively a valve piston 61 provided with valveland portions 61a and 61b near its extremities for slidably engaging thebody portion 60 so as to form fluid seals therebetween. Near the middleof the valve piston 61 is a third valve land portion 610 normallyclosing or lapping passageway 62 to which leads the header 56. It willbe observed that the diameter of the piston 61 is substantially reducedbetween the land portions 61a and 610 (aligned with passageway 63) andbetween the land portions 610 and 61b (aligned with passageway 64).

Accordingly, it will be seen that if the piston 61 is moved downwardly,the movement of the land portion 610 will uncover the passageway 62,thereby atfording fluid communication from the control supply header 49through the passageway 63, the interior of the valve 45, the passageway62, and the automatic control header 56 to the actuating air pressureheader 57. Conversely, upward movement of the piston 61 results inupward movement of the land portion 610, so as to permit venting of airpressure through the passageway 62, the interior of the valve 45, andthe venting passageway 64 to atmosphere.

As appears in FIGURE 1, the signal air pressure header 51 communicateswith a top diaphragm chamber 67 by means of the signal header 50. As canbe appreciated, an increase in the signal air pressure thus beingintroduced into the top diaphragm chamber 67 acts against top diaphragm70 so as to move the piston 61 upwardly and thereby to effectively ventsome of the air pressure in the headers 56 and 57. It will thus be seenthat an increase in tension on the web 11 causes an increase in thesignal air pressure, which in turn actuates the valve 45 so as to effecta decrease in the actuating air pressure communicating with the airbrake 37, essentially as is described in my earlier patent.

Above and in contact with the top diaphragm there is positioned anadjustable spring 71 so as to resist upward movement thereof in responseto signal air pressure increases. The spring 71 may be adjustably set asby screw means 71a to resist movement of the diaphragm 70 to apredetermined extent.

A bottom diaphragm 72 is mounted at the bottom of the piston 61, andseparates an upper diaphragm chamber 73 from a lower diaphragm chamber74. The signal air pressure header 51 communicates through the header 52with the lower diaphragm chamber 74, and also connected to the header 51through the header 53 is the noted surge tank. Suitable throttle valvingwould of course normally be employed in the header 53, and as appears inFIGURE 2, the surge header 55 conununicates with the upper diaphragmchamber 73.

In this manner and during automatic operation an increase in the signalair pressure in the header 51 effects an increase in the air pressure inthe lower diaphragm chamber 74 by means of the signal header 52. At thesame time, the increase in air pressure in the header 51 begins toincrease the pressure in the surge tank 54 by bleeding through thementioned throttle valve means 53a. In a comparatively short time thepressure in the surge tank 54 reaches a pressure that is the same asthat in the header 51, and accordingly, the surge tank signal header 55permits an equalizing pressure to be formed in the diaphragm chamber 73,thereby tending to return the piston 61 to its original position. Inthis manner, the piston 61 may be started back to its original positionbefore it has a chance to produce a change in the actuating air pressureagainst the air brake member 37 that is greater than that necessary tocorrect the tension on the web 11.

While the arrangement thus far described possesses many advantages overearlier unwinding systems, it has been found that improvements can bemade therein to prevent breakage of or damage to a relatively lightsheet by acceleration forces, as well as to produce a constant tensionon the sheet during acceleration. As was earlier explained, if tensionin the traveling paper web 11 increases the signal air pressure in theheader 51 increases to actuate the valve 45 and thereby decrease theactuating air pressure communicated by the header 57 to the air brake37. Under these circumstances the modulation output provided by thecontrol system just described would be less than the constant forceoutput and the brake is released; however, the unwind roll 10 would havesufiicient inertial resistance to rotation to cause at least damage tothe web, if not breakage thereof. Particularly is this the case withrelatively light sheets, webs or strands.

However, by this invention the acceleration rate of the rewind roll 18is controlled by the same actuating air pressures which are in controlof the air brake 37. Simply stated, in accordance with this inventionwhen the modulating output to the air brake 37 is at or below therequired positive output for zero braking effort, the current supply togenerator means supplying the drive means 21 and 22 is modulated so thatthe power available to the drive rolls 19 and 20 is controlled toprovide a constant sheet tension.

In this manner a smooth stepless transition of the tension control ismade which matches the productive speed of the machine in accordancewith either the inertia or drag of the supply means.

. Referring now again to FIGURE 1, the control header 56 has a secondconnection 75 communicating therewith which terminates in a fluidpressure operated device 76 forming a part of the pressure responsiveelectrical control means of this invention and generally designated bythe numeral 77. The device 76 may be seen to comprise a cylinder 78housing for reciprocal movement piston means 79 to which is connectedrod means 80 carrying at its opposite end a rack gear 81. The cylinder78 defines therewithin a piston chamber 78a, and resiliently urging thepiston 79 to a return position is spring means 82 mounted in encirclingrelation to the rod member 80.

The rack gear 81 meshes with a pinion gear 81a mechanically connected toa moveable contact 83 of a potentiometer 84, as is indicated by thedotted line. The contact 83 is connected to terminal 85 of .a controlunit 86, while the end terminals of the potentiometer are connected toterminals 87 and 88 of the unit 86. The control unit 86 has power inputterminals 89 and 90 connected to output conductors 91 and 92 ofgenerator means 93. The output conductors 91 and 92 are connected to themotors 21 and 22, together with a third output conductor 94. Thegenerator 93 is driven by a motor 95 or other motive power source, .asdiagrammatically illustrated.

The control unit 86 has output terminals 96 and 97 connected to a fieldwinding 98 of the generator 93. The control unit 86 may comprise asuitable amplifier, the output of which is controlled by the position ofthe potentiometer contact 83. In the alternative, the potentiometer 84-may be connected as a rheostat directly between the input terminals 89and 90 and output terminals 96 and 97, to directly control the generatorexitation.

While the operation of the instant tension control system is believedquite apparent from the preceding description, a brief summary will nowbe given. Assuming first that the spring means 39 of the friction brakearrangement 24 absorbs pounds per square inch and that the brakingoutput of the air brake 37 is within the range of from 10 to 50 poundsper square inch, if the braking pressure supplied through the actuatingair header 57 is at 10 pounds per square inch or more, a similar amountof pressure is supplied through the valve means 45 to the conduit 75 andfluid pressure operated device 76. This causes downward movement of thepiston 79 to move the potentiometer contact 83 to a maximum orapproaching maximum current setting, depending of course upon theparticular pressure values applied. The generator 93 is thereby excitedthrough its field winding 98 at a relatively high level, to providethrough the generator conductors 91, 92 and 94 a relatively high outputto the motor means 21 and 22., so that suflicient power is delivered bythe motor means to the drive rolls 19 and 20, assuring sufiicientacceleration of the rewind roll 18 to maintain constant tension in thetraveling sheet or web 11.

On the other hand, and again assuming the same braking effort values, ifthe actuating air pressures supplied through the header 57 to the airbrake 37 Vary from 10 psi. to 0 p.s.i., substantially the same airpressures are supplied to the device 76 to modulate the current settingand thereby assure that the power supplied by the motor means 21 and 22is at a sufliciently low level to again prevent a mismatchedacceleration and sheet damage or breakage.

As well, by provision of the disclosed system in control of theacceleration of the rewind roll 18, substantially greater accelerationrates can be employed with smaller unwind rolls than with larger unwindrolls, without encountering damage or breakage problems. As was statedin the early portions of this specification, the acceleration torquerequired to overcome inertia of the unwind roll is a product of webtension and roll radius. Since the permissible web tension is a knownvalue as limited by the inherent strength of a particular web, itfollows that as the radius of the unwind roll is reduced, an increase inacceleration is permitted. In this manner, various size rolls can beaccommodated on the same apparatus, thereby increasing its versatility,or as the radius of a particular unwind roll is reduced during theunwinding of web material therefrom, the acceleration forces applied tothe rewind roll can be increased, to produce the important benefit ofmarkedly increased production.

It is of course to be appreciated that a hydraulic system could beemployed in substitution for the disclosed pneumatic system, .and thatthe pressure responsive electrical control means 77 can be constitutedin ways diflerent from that specifically disclosed. It also will beevident that the system described is not limited in its application towinding machines but is of equal utility in control of web tension fromany web supplying unit to any web fed unit such as coating or printingapparatus. These and other modifications can accordingly be effectedwithout departing from the novel concepts of this invention.

I claim as my invention:

1, Means for controlling the tension on sheet material being unwoundfrom a roll, comprising a fluid pressure responsive brake for the roll,a fluid pressure source, a fluid pressure responsive valve in control ofcommunication between the brake and source applying a fluid pressure tothe brake, valve means responsive to the tension on the sheet materialfor imparting fluid pressure to the fluid pressure responsive valve, andpressure responsive electrical control means operatively connected tothe fluid pressure responsive valve for modulating the acceleration ofthe roll in accordance with the fluid pressure applied to the brake.

2. Tension control means for sheet material, comprising a supply roll, adelivery roll, driving means for the delivery roll, a fluid pressureresponsive brake for the supply roll, means responsive to variations inthe sheet tension for controlling the fluid pressure input to the brake,and means responsive to variations in the fluid pressure input to thebrake and connected to said driving means for controlling theacceleration of the delivery roll.

3. Tension control means for sheet material, comprising a supply roll, adelivery roll, brake means for the supply roll, drive means for thedelivery roll, means responsive to variations in the tension of thesheet material for varying the braking eflort of the brake means, andrheostat means mechanically connected to the brake means and to themeans for varying the braking eflort thereof and electrically connectedto the drive means for controlling the acceleration of the delivery rollin response to variations in the braking eliort.

4. Tension control means for sheet material, comprising an unwind roll,a rewind roll, a fluid pressure responsive brake for the unwind roll,drive means for the rewind roll, a fluid pressure source, a fluidpressure responsive valve in control of communication between the brakeand source, valve means responsive to the tension on the sheet materialfor imparting fluid pressure to the fluid pressure responsive valve, andfluid pressure operated rheostat means in fluid communication with thebrake and with the fluid pressure responsive valve and electricallyconnected to the drive means for controlling the acceleration of therewind roll in response to the fluid pressures applied to the brake.

5. Tension control means for sheet matteriral, comprising an unwindroll, a rewind roll, a fluid pressure responsive brake for the unwindroll, drive means for the rewind roll, a fluid pressure source, a fluidpressure responsive valve in control of communication between the brakeand source, valve means responsive to the tension on the sheet materialfor imparting fluid pressure to the fluid pressure responsive valve,fluid pressure responsive actuating means in fluid communication withthe brake and with the fluid pressure responsive valve, and rheostatmeans mechanically connected to the actuating means and electricallyconnected to the drive means for controlling the acceleration of therewind roll in response to the fluid pressures applied to the brake.

6. Tension controlmeans for sheet material, compris= ing an unwind roll,a rewind roll, drive means for said rewind roll, a fluid pressureresponsive brake for said unwind roll, a fluid pressure responsive valvein control of fluid communication between said brake and a source, bleedvalve means presenting a leakage aperture adapted to engage the sheetmaterial, conduit means connecting said bleed valve means to saidpressure responsive valve and said latter valve to said brake, generatormeans electrically connected to said' drive means, and pressureresponsive electrical control means in fluid communication with saidpressure responsive valve means controlling the current input to saidgenerator means in accordance with the pressure applied to said unwindroll by said brake.

7. Tension control means for sheet material, comprising an unwind roll,a rewind roll, drive means for said rewind roll, a fluid pressureresponsive brake for said unwind roll, a fluid pressure responsive valvein control of fluid communication between said brake and a source, bleedvalve means presenting a leakage aperture adapted to engage the sheetmaterial, conduit means connecting said bleed valve means to saidpressure responsive valve and said latter valve to said brake, generatormeans electrically connected to said drive means, and fluid pressureoperated rheostat means in fluid communication With the brake and withthe fluid pressure responsive valve and electrically connected to thegenerator means for varying the current input to the generator means andthe power delivered by the drive means to control the acceleration ofthe rewind roll in response to the fluid pressures applied to the brake.

8. Tension control means for sheet material, comprising an unwind roll,a rewind roll, drive means for said rewind roll, a fluid pressureresponsive brake for said unwind roll, a fluid pressure responsive valvein control of fluid communication between said brake and a source,

bleed valve means presenting a leakage aperture adapted to engage thesheet material, conduit means connecting said bleed valve means to saidpressure responsive valve and said latter valve to said brake, generatormeans electrically connected to said drive means and having -a fieldwinding therein, fluid pressure responsive actuating means in fluidcommunication with the brake and with the fluid pressure responsivevalve, rheostate means mechanically connected to the actuating means,and amplifier means electrically connected to said rheostat means and tosaid field winding, said actuating means being actuated in response tothe fluid pressures applied to the brake to vary the current setting ofthe rheostat means, thereby modulating the power supplied by thegenerator means to the drive means for controlling the acceleration ofthe rewind roll.

9. Means for controlling tension in a sheet travelling from a supplymeans to a takeup means, comprising drive means for said takeup means, afluid pressure source, a pressure control header, a fluid pressureresponsive valve in control of communication between the header and thesource applying fluid pressure to the header, valve means responsive tothe tension on the sheet for imparting actuating fluid pressure to saidfluid pressure responsive valve, means for controlling said supply meansin response to fluid pressure in said hearer, and means connected tosaid drive means for controlling said drive means in response to fluidpressure variation in said header.

References Cited in the file of this patent UNITED STATES PATENTS2,469,706 Winther May 10, 1949 2,755,032 Justus July 17, 1956 2,925,963De Gelleke Feb. 23, 1960 2,983,463 Aaron et a1. May 9, 1961

